CROSS-REFERENCE TO RELATED APPLICATION
The following application is related to co-pending application, entitled "Flash ROM Programmer," by Clark Buxton, Ser. No. 07/885,805, filed on May 15, 1992 and co-pending application, entitled "Memory System," by Min E. Lee and Jiming Sun, Ser. No. 07/995,803 filed on Dec. 23, 1992.
1. Field of the Invention
The present invention relates to a method and apparatus for upgrading a Basic Input Output System (BIOS) for a computer system stored on a system mass storage device, such as a disk drive, without changing any hardware which obviates the need for partitioning the disk or providing for disaster recovery which enables the computer system to be booted in the event of a disk failure.
2. Description of the Prior Art
Various methods and systems are known for upgrading the BIOS in a computer system. In earlier personal computers, the BIOS was loaded into a programmable read only memory (PROM) or an ultraviolet erasable electrically programmable ROM (EPROM). In such systems, since the BIOS is very hardware specific, any changes in the computer hardware normally required the BIOS to be upgraded. Such upgrades required that the computer case be opened and the PROM or EPROM chip containing the BIOS to be removed and replaced with a new PROM or EPROM chip containing the updated BIOS. In such a situation, the replacement of the BIOS was known to require the services of a computer technician which can be relatively expensive.
In other known systems, such as the system disclosed in co-pending application, Ser. No. 07/995,803, filed on Dec. 23, 1992, assigned to the same Assignee as the Assignee of the present invention, the BIOS is loaded into flash ROM. Flash ROM is relatively expensive, which drives up the cost of the computer system. In addition, the boot block portion of the flash ROM has a limited size which limits the number of BIOS functions that can be stored. Such flash ROMs also require programming circuitry which, inter alia, requires a 12-volt programming voltage in order to program the flash ROM in contradistinction to a ROM or EPROM which does not require programming circuitry, since such devices are normally programmed outside the computer system. Moreover, relatively complex disaster recovery is required to enable the system to be rebooted in the event of a failure of the flash ROM device.
In yet other known systems, the BIOS is loaded into a protected area of a hard disk. Examples of such systems are disclosed in U.S. Pat. Nos. 4,928,237; 5,022,077; 5,063,496; 5,072,370; 5,128,995; and 5,136,713, as well as European Patent Application No. 0 479 427 A2, all herein incorporated by reference. In such systems, basic start-up BIOS functions are provided on a ROM with the balance of the BIOS function stored on the hard disk and written to main memory during the start-up sequence. In such an application, the BIOS is normally loaded onto a protected area of the hard disk, thus reducing the disk space available for other applications. In addition, such computer systems will not boot when the hard drive fails in such systems. As such, no diagnostic utilities can be utilized to ascertain the source of the disk failure.
In order to reduce costs, it is also known to utilize a MASKED ROM, fabricated with the BIOS code already stored, also known as a MASKED device. Such MASKED devices are relatively inexpensive and obviate the need for programming circuitry. However, the use of such MASKED devices can have a dilatory impact on the development and production schedule of a computer system due to the relatively long lead time (i.e., 6-8 weeks) to obtain such devices, often necessitating the use of the more expensive memory devices such as one time programmable (OTP) memory devices which typically cost less than EPROM, EEPROM and flash ROM memory devices. More particularly, since the MASKED and OTP devices cannot be reprogrammed after fabrication, the commercial version of MASKED devices are normally ordered relatively late in the production cycle of a computer system. The relatively long lead time of such MASKED devices thus undesirably extends the development and production cycle of the computer system into which the MASKED device is being incorporated. In addition, since such MASKED devices are normally ordered in relatively large quantities, many of such devices normally end up as surplus.